Identifying Weeds

There are a number of invasive plant species living and growing in the Municipal District of Bonnyville. Through a feature on our Facebook page, we are helping spread the word about these species. This page will be updated a couple of times a month to coincide with the Facebook posts #WeedWednesday.

The information on this page has been provided by the Alberta Invasive Species Council, unless otherwise noted. 

Plant Name:

Oxeye Daisy (leucanthemum vulgare)Oxeye Daisy 3

Identification:

Stems: Grow up to one metre tall and are smooth, frequently grooved and sometimes branch near the top (although more frequently unbranched).

Leaves: Progressively decrease in size upward on the stem. Basal and lower leaves are lance-shaped with “toothed” margins and petioles that may be as long as the leaves. The upper leaves are alternately arranged, narrow and often clasp the stem with wavy margins. 

Flowers: Are borne singly at the end of stems and can be up to five centimetres in diameter, with yellow centres, and 20 to 30 white petals radiating from the centre. The petals are slightly notched at the tip.

Prevention:

The availability of closely related plants through the nursery and seed trade contradicts the perception of Oxeye as an invasive plant, and subsequent control. Shasta daisy is a cultivar (originated from) of Oxeye sold through nurseries and as seed in wildflower mixes. This fact makes public awareness critical to prevention and control. The two plants can cross breed, resulting in an invasive hybrid that is extremely difficult to distinguish from either parent. Invasive ornamentals can be very difficult to contain and should be avoided. Consumers should carefully read the contents of so-called ‘wildflower’ seed mixes and avoid those containing invasive ornamentals.

Control:

Grazing: Oxeye Daisy is avoided by cattle and therefore capable of dominating pastures and rangeland. Horses, sheep and goats, however, will readily graze oxeye daisy and can be used in companion grazing situations to control oxeye daisy. Switching to higher stock densities and shorter grazing periods does encourage cattle to eat and trample more of the plant. Intensive grazing and trampling slightly reduces the number of seeds produced, and presumably injures younger rootstalks. Trampling also brings dormant seeds to the surface and removes the canopy cover so those seeds will germinate with mid-summer rain showers. In normal years, those seedlings will dry-out and die before becoming established, further reducing the number of seeds in the seed bank. It should be noted, however, that intensive grazing in wet summers may increase the number of successful seedlings. As many as 40% percent of the seeds consumed by cattle may remain viable after passing through the digestive tract, so care should be taken to avoid spreading the seeds when moving stock.

Mechanical: Repeated mowing prevents seed production, but also can stimulate re-sprouting of stems. Hand-pulling or digging before seed production is effective, but it is important to remove as much of the fibrous roots and rhizomes as possible. Ground disturbance while digging should be kept to a minimum. Hand removal will have to be continued for several years because seeds may remain viable in the soil for a long time. Because of its shallow root system, oxeye daisy is easily killed by intensive cultivation. 

Chemical: Aminopyralid alone or in a product mix with Metsulfuron-methyl or 2,4-D is registered for use on oxeye daisy. Always check product labels to ensure the herbicide is registered for use on the target plant in Canada by the Pest Management Regulatory Agency. Always read and follow label directions. Consult your local Agricultural Fieldman or Certified Pesticide Dispenser for more information. 

Biological: In 2008 a literature study was conducted to investigate European insect species that feed on oxeye daisy. Studies on ploidy analysis, to be conducted by CABI, and molecular analysis, to be conducted by USDA-ARS, are underway with field collected and commercially available Shasta daisy cultivars to determine the relationship with the target oxeye daisy and assist in host range understanding of potential biocontrol agents. An international consortium, including the Alberta Invasive Species Council, is funding research at CABI1.

Plant Name:

Scentless Chamomile (Tripleurospermum perforatum)

Scentless Chamomile 3Identification: 

Stems: Stems are erect to semi-erect, highly branched, may be reddish in color, and can grow up to 1 m tall. There can be a few to many stems per plant. 

Leaves: Leaves are alternate and very finely divided into short segments (carrot-like) and odorless when crushed. Basal leaves disappear by flowering time. 

Flowers: Flowers are composed of a yellow central disk surrounded by white petals. The flowers are borne singly at the end of stems and have numerous bracts, arranged in overlapping rows. 

Seeds: Seeds are tiny (about 2 mm), ribbed and dark brown. Seeds develop and become viable quickly

Prevention:

Scentless Chamomile does not compete well with vigorous, healthy plant communities. Dispersal by weed seed contamination in crop/grass seed and livestock forage is common. It can be very difficult to eradicate in crop situations.

Control:

Grazing: Scentless chamomile is generally unpalatable to grazers and its seeds can survive digestion. Invasive plants should never be considered as forage. 

Cultivation: Late fall and early spring tillage will control rosettes. Frequent, shallow tillage can help exhaust the seed bank by repeatedly destroying germinating seedlings. Equipment must be cleaned after. 

Mechanical: Mowing can prevent seed production but plants will re-bloom below the cutting height. Hand-pulling can prevent spread into new areas and is effective on small infestations. Pulled plants should be burned or bagged and sent to the landfill. Burning infestations that have finished blooming can prevent seed spread.

Chemical: Aminopyralid (alone or in a product mix with 2,4-D or Metsulfuron-methyl), Chlorsulfuron, Clopyralid (alone or in a product mix with MCPA), Dicamba, Glufosinate ammonium, Hexazinone, Picloram, MCPA (in a product mix with Bromoxynil), Metsulfuron-methyl and Tribenuron-methyl (in a product mix with Thifensulfuron-methyl) are registered for use on scentless chamomile. Always check product labels to ensure the herbicide is registered for use on the target plant in Canada by the Pest Management Regulatory Agency. Always read and follow label directions. Consult your local Agricultural Fieldman or Certified Pesticide Dispenser for more information.

Biological: A seed-head feeding weevil, Omphalapion hookeri, and a gall midge, Rhopalomyia tripleurospermi, have been released in Alberta.